lob0pages.h

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#ifndef lob0pages_h
#define lob0pages_h
 
#include "lob0first.h"
 
namespace lob {
 
/** The LOB data page carrying the user data. */
struct data_page_t : public basic_page_t {
  static const ulint OFFSET_VERSION = FIL_PAGE_DATA;
  static const ulint OFFSET_DATA_LEN = OFFSET_VERSION + 1;
  static const ulint OFFSET_TRX_ID = OFFSET_DATA_LEN + 4;
  static const ulint LOB_PAGE_DATA = OFFSET_TRX_ID + 6;
 
  data_page_t() = default;
 
  /** Constructor. */
  data_page_t(buf_block_t *block, mtr_t *mtr) : basic_page_t(block, mtr) {
    page_type_t type = get_page_type();
    ut_a(type == FIL_PAGE_TYPE_LOB_DATA);
  }
 
  data_page_t(buf_block_t *block, mtr_t *mtr, dict_index_t *index)
      : basic_page_t(block, mtr, index) {}
 
  data_page_t(mtr_t *mtr, dict_index_t *index)
      : basic_page_t(nullptr, mtr, index) {}
 
  /** Constructor.
  @param[in]    block   the buffer block.*/
  data_page_t(buf_block_t *block) : basic_page_t(block, nullptr, nullptr) {}
 
  /** Allocate a LOB data page.
  @param[in] alloc_mtr  Mini-transaction to be used for allocation of LOB page.
  @param[in] is_bulk    true if bulk operation.
  @return allocated buffer block or nullptr */
  buf_block_t *alloc(mtr_t *alloc_mtr, bool is_bulk);
 
  buf_block_t *load_x(page_no_t page_no);
 
  void set_version_0() {
    mlog_write_ulint(frame() + OFFSET_VERSION, 0, MLOG_1BYTE, m_mtr);
  }
 
  void dealloc() {
    btr_page_free_low(m_index, m_block, ULINT_UNDEFINED, m_mtr);
    m_block = nullptr;
  }
 
  void set_page_type() {
    ut_ad(m_mtr != nullptr);
 
    mlog_write_ulint(frame() + FIL_PAGE_TYPE, FIL_PAGE_TYPE_LOB_DATA,
                     MLOG_2BYTES, m_mtr);
  }
 
  void set_trx_id(trx_id_t id) {
    byte *ptr = frame() + OFFSET_TRX_ID;
    mach_write_to_6(ptr, id);
    mlog_log_string(ptr, 6, m_mtr);
  }
 
  /** Write the trx identifier to the header, without
  generating redo log.
  @param[in]    id      the transaction identifier.*/
  void set_trx_id_no_redo(trx_id_t id) {
    byte *ptr = frame() + OFFSET_TRX_ID;
    mach_write_to_6(ptr, id);
  }
 
  static ulint payload() {
    return (UNIV_PAGE_SIZE - LOB_PAGE_DATA - FIL_PAGE_DATA_END);
  }
 
  byte *data_begin() const { return (frame() + LOB_PAGE_DATA); }
 
  /** Create a new data page and replace some or all parts of the old data
  with data.
  @param[in]      trx     Current transaction.
  @param[in]      offset  Offset where replace begins.
  @param[in,out]  ptr     Pointer to new data.
  @param[in]      want    Amount of data the caller wants to replace.
  @param[in]      mtr     Mini-transaction context.
  @return the buffer block of the new data page. */
  buf_block_t *replace(trx_t *trx, ulint offset, const byte *&ptr, ulint &want,
                       mtr_t *mtr);
 
  /** Replace some or all parts of the data inline.
  @param[in]      offset  Offset where replace begins.
  @param[in,out]  ptr     Pointer to new data.
  @param[in]      want    Amount of data the caller wants to replace.
  @param[in]      mtr     Mini-transaction context. */
  void replace_inline(ulint offset, const byte *&ptr, ulint &want, mtr_t *mtr);
 
  ulint get_data_len() const {
    return (mach_read_from_4(frame() + OFFSET_DATA_LEN));
  }
 
  void set_data_len(ulint len) {
    ut_ad(m_mtr != nullptr);
 
    mlog_write_ulint(frame() + OFFSET_DATA_LEN, len, MLOG_4BYTES, m_mtr);
  }
 
  /** Read data from the data page.
  @param[in]    offset  read begins at this offset.
  @param[out]   ptr     the output buffer.
  @param[in]    want    bytes to read
  @return bytes actually read. */
  ulint read(ulint offset, byte *ptr, ulint want);
 
  /** Write data into a data page.
  @param[in,out]        data    the data to be written.  it will be updated to
  point to the byte not yet written.
  @param[in,out]        len     length of data to be written.
  @return amount of data actually written into the page. */
  ulint write(const byte *&data, ulint &len);
 
  /** Append given data in data page.
  @param[in]    trxid   transaction doing append.
  @param[in,out]        data    data to be appended.
  @param[in,out]        len     length of data.
  @return number of bytes appended. */
  ulint append(trx_id_t trxid, byte *&data, ulint &len);
 
  std::pair<ulint, byte *> insert_middle(trx_t *trx, ulint offset, byte *&data,
                                         ulint &len, buf_block_t *&new_block);
 
  buf_block_t *remove_middle(trx_t *trx, ulint offset, ulint &len);
 
  ulint max_space_available() const { return (payload()); }
 
  ulint space_left() const;
};
 
} /* namespace lob */
 
#endif /* lob0pages_h */